Prevention of Tuberculosis with Isoniazid (INH)
My chest X-ray is normal and I feel fine. What is the significance of my positive skin test or blood test?
The good news is that you do not have active tuberculosis, an infectious disease that kills more people each year than almost any other. However, a positive tuberculin skin test or positive Quantiferon TB test indicates prior exposure to the tuberculosis germ. This germ has been known to lay latent in the body for months to decades before it becomes active and causes serious illness. If you have never been treated for your positive test, then you have latent tuberculosis and are at risk of developing active tuberculosis later.
I was vaccinated as a child against tuberculosis. I’ve heard that vaccination can cause a falsely positive skin test. Why am I at risk of contracting the disease from which I thought I was protected?
The tuberculosis vaccination, also known as BCG, does help to protect children against serious tubercular disease. But, it doesn’t protect adults. It is true that BCG can sometimes cause a falsely positive skin test, though this is much more likely to happen in children than in adults. The Quantiferon TB blood test, however, does not become positive because of BCG vaccination. Therefore, this test has become our tuberculosis screening test of choice for those who were vaccinated with BCG.
I don’t want to have latent tuberculosis. How do I make it go away?
Latent tuberculosis is simply treated by taking a tablet of Isoniazid (INH) once a day for at least 6 months. This will kill any tuberculosis bacteria that may be lying dormant in the body. INH is used because it is affordable, effective, well-tolerated and side effects are unlikely.
Am I required to take Isoniazid to stay at the university?
There is no requirement that students with latent tuberculosis take any treatment for latent tuberculosis (isolation and treatment is required for active tuberculosis.) However, your doctors at the health center hope that you will want the treatment so that you do not become ill while you are at the university or afterwards. Should you become sick, you are also likely to make others who live with you sick with a very serious illness that you could have easily prevented.
It is reassuring to hear that Isoniazid is usually well tolerated. I have no time to be sick. What would happen if I had a problem?
The most common side effect from INH is temporary mild stomach upset. If it happens, it can usually be prevented by taking it with food. Serious side effects are rare and include liver inflammation, allergic-type reactions and sensory nerve problems. Vitamin B6 (pyridoxine) decreases the risk of nerve problems so we also prescribe a vitamin B6 tablet to take with INH. Before you start your INH, we will provide you with a list of symptoms to contact us about should you experience them, and we will want to see you every month or two while you are taking it. If you are experiencing anything more than a minor side effect, we will discontinue your treatment.
I take other medications and vitamins. Will I still be able to take them?
INH is compatible with most medications and vitamins, but we should review your medication list before you start.
I am more than 35 years old. Are there any special precautions for me?
The risk of liver problems, though it remains low, increases with age. Those more than 35 years old frequently have a blood test every month or two to check for significant increases in liver enzymes.
I am pregnant. Should I take INH?
You should delay your treatment until after you deliver your baby and complete nursing.
What is the cost of treatment?
We charge $5 for each month’s worth of INH, but do not charge for office visits, any lab tests resulting from treatment or for Vitamin B6.
I am on campus for a semester or less. Should I start my INH, now?
You could start now, but you probably should delay treatment until later.
I have other questions. I’d also like to talk with my home doctor and parents before I decide.
Great. We want to answer any questions that you may have. We encourage you to also talk with the healthcare provider that your family trusts for advice.
References
Centers for Disease Control Tuberculosis (TB) web site: http://www.cdc.gov/tb
Pai, M. & Menzies, R. Diagnosis of latent tuberculosis infection in adults. Feb 2010. UpToDate Online 18.2. May 2010.
